1、BRITISH STANDARDBS EN 60068-3-4:2002IEC 60068-3-4:2001Incorporating Corrigendum No. 1Environmental testing Part 3-4: Supporting documentation and guidance Damp heat testsThe European Standard EN 60068-3-4:2002:2002 has the status of a British StandardICS 19.040; 19.080g49g50g3g38g50g51g60g44g49g42g3
2、g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN 60068-3-4:2002This British Standard, having been prepared under the direction of the Electrotechnical Sector Policy and Strat
3、egy Committee, was published under the authority of the Standards Policy and Strategy Committee on 21 March 2002 BSI 19 January 2006ISBN 0 580 39112 4National forewordThis British Standard is the official English language version of EN 60068-3-4:2002. It is identical with IEC 60068-3-4:2001. It supe
4、rsedes The UK participation in its preparation was entrusted to Technical Committee GEL/10, Environmental conditions, classification and testing, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary.From 1 January 1997, al
5、l IEC publications have the number 60000 added to the old number. For instance, IEC 27-1 has been renumbered as IEC 60027-1. For a period of time during the change over from one numbering system to the other, publications may contain identifiers from both systems.Cross-referencesThe British Standard
6、s which implement these international or European publications may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue.A British Standard does not purport to inclu
7、de all the necessary provisions of a contract. Users of British Standards are responsible for their correct application.Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/Europea
8、n committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK.Summary of pagesThis document comprises a front cover, an inside front cover, the EN title page, pages 2
9、 to 16, an inside back cover and a back cover.The BSI copyright date displayed in this document indicates when the document was last issued.Amendments issued since publicationAmd. No. Date Comments15889 Corrigendum No. 119 January 2006 Addition of supersession detailsBS 2011-2.2 C and D:1990 which i
10、s withdrawn.EUROPEAN STANDARD EN 60068-3-4NORME EUROPENNEEUROPISCHE NORM January 2002CENELECEuropean Committee for Electrotechnical StandardizationComit Europen de Normalisation ElectrotechniqueEuropisches Komitee fr Elektrotechnische NormungCentral Secretariat: rue de Stassart 35, B - 1050 Brussels
11、 2002 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.Ref. No. EN 60068-3-4:2002 EICS 19.040;29.020 Supersedes HD 323.2.28 S1:1988English versionEnvironmental testingPart 3-4: Supporting documentation and guidance Damp heat tests(IEC 60068-3-4
12、:2001)Essais denvironnementPartie 3-4: Documentationdaccompagnement et guide Essais de chaleur humide(CEI 60068-3-4:2001)UmweltprfungenTeil 3-4: UntersttzendeDokumentation und Leitfaden Prfungen mit feuchter Wrme(IEC 60068-3-4:2001)This European Standard was approved by CENELEC on 2001-12-04. CENELE
13、C members are bound tocomply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration.Up-to-date lists and bibliographical references concerning such national standards may be obtained onapplica
14、tion to the Central Secretariat or to any CENELEC member.This European Standard exists in three official versions (English, French, German). A version in any otherlanguage made by translation under the responsibility of a CENELEC member into its own language andnotified to the Central Secretariat ha
15、s the same status as the official versions.CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,Norway, Portugal, Spain, Sweden, Switzerland and United Kingd
16、om.IncForewordThe text of document 104/208/FDIS, future edition 1 of IEC 60068-3-4, prepared by IEC TC 104,Environmental conditions, classification and methods of test, was submitted to the IEC-CENELECparallel vote and was approved by CENELEC as EN 60068-3-4 on 2001-12-04This European Standard super
17、sedes HD 323.2.28 S1:1988.The following dates were fixed: latest date by which the EN has to be implementedat national level by publication of an identicalnational standard or by endorsement (dop) 2002-09-01 latest date by which the national standards conflictingwith the EN have to be withdrawn (dow
18、) 2004-12-01Annexes designated “informative“ are given for information only. In this standard, annex A is informative._Endorsement noticeThe text of the International Standard IEC 60068-3-4:2001 was approved by CENELEC as aEuropean Standard without any modification.In the official version, for Bibli
19、ography, the following notes have to be added for the standardsindicated:IEC 60068-1 NOTE Harmonized as EN 60068-1:1994 (not modified).IEC 60068-2-1 NOTE Harmonized as EN 60068-2-1:1993 (not modified).IEC 60068-2-10 NOTE Harmonized as HD 323.2.10 S3:1988 (not modified).IEC 60068-2-14 NOTE Harmonized
20、 as EN 60068-2-14:1999 (not modified).IEC 60068-2-17 NOTE Harmonized as EN 60068-2-17:1994 (not modified).IEC 60068-2-30 NOTE Harmonized as EN 60068-2-30:1999 (not modified).IEC 60068-2-38 NOTE Harmonized as EN 60068-2-38:1999 (not modified).IEC 60068-2-39 NOTE Harmonized as EN 60068-2-39:1999 (not
21、modified).IEC 60068-2-61 NOTE Harmonized as EN 60068-2-61:1993 (not modified).IEC 60068-2-66 NOTE Harmonized as EN 60068-2-66:1994 (not modified).IEC 60068-2-67 NOTE Harmonized as EN 60068-2-67:1996 (not modified).IEC 60068-2-78 NOTE Harmonized as EN 60068-2-78:2001 (not modified)._Page 2EN 6006834:
22、2002CONTENTSINTRODUCTION 41 Scope 52 Definitions 53 Procedures for the production and control of humidity. 63.1 General 63.2 Injection of water (spraying) 63.3 Injection of water vapour (steam) 63.4 Saturation type 63.5 Surface evaporation 63.6 Aqueous solutions. 73.7 Dehumidification . 73.8 Control
23、 of humidity 74 Physical appearance of the effects of humidity . 74.1 Condensation 74.2 Adsorption 84.3 Absorption 84.4 Diffusion . 85 Acceleration. 85.1 General 85.2 Acceleration factor 96 Comparison of steady-state and cyclic tests . 96.1 Test C: Damp heat, steady-state . 96.2 Test Db: Damp heat,
24、cyclic test. 96.3 Sequences of tests and composite tests 97 Influence of test environment on specimens 107.1 Change of physical characteristics .107.2 Change of electrical characteristics 107.3 Corrosion.11Annexe A (informative) Humidity effects diagram 12Bibliography 16Figure A.1 Physical processes
25、 involved in humidity testing14Page 3EN 6006834:2002INTRODUCTIONTemperature and relative humidity (RH) of the air, in varying combinations, are climatic factorswhich act upon a product during storage, transportation and operation.Meteorological measurements made over many years have shown that a rel
26、ative humidity95 % combined with a temperature 30 C does not occur in free air conditions over longperiods, except in regions with extreme climates. In dwelling rooms and workshopstemperatures of 30 C may occur but in most cases are combined with a lower relativehumidity than in the open air.Special
27、 conditions exist in certain wet rooms for example, in the chemical industry,metallurgical plants, mines, electroplating plants and laundries, where the temperature canreach 45 C combined with a relative humidity up to saturation over long periods.Certain equipment placed under particular conditions
28、 may be subjected to relative humidities ofmore than 95 % at higher temperatures. This may happen when the equipment is placed inenclosures, such as vehicles, tents or aircraft cockpits, since this can result in intense heatingthrough solar radiation while, because of inadequate ventilation, any hum
29、idity that may bedeveloped will be retained permanently within the interior.In rooms having several heat sources, temperatures and relative humidities may vary indifferent parts of the room.Atmospheric pollution can intensify the effects of a damp climate on products. Attention isdrawn to this fact
30、because of its general importance, although pollutants are not contained inthe atmospheres used for damp heat testing. If the effects of pollutants, for example corrosionand mould growth, are to be investigated, a suitable test from the IEC 60068-2 series shouldbe used.Page 4EN 6006834:2002ENVIRONME
31、NTAL TESTING Part 3-4: Supporting documentation and guidance Damp heat tests1 ScopeThis part of IEC 60068 provides the necessary information to assist in preparing relevantspecifications, such as standards for components or equipment, in order to select appropriatetests and test severities for speci
32、fic products and, in some cases, specific types of application.The object of damp heat tests is to determine the ability of products to withstand the stressesoccurring in a high relative humidity environment, with or without condensation, and withspecial regard to variations of electrical and mechan
33、ical characteristics. Damp heat tests mayalso be utilized to check the resistance of a specimen to some forms of corrosion attack.2 DefinitionsFor the purpose of this part of IEC 60068, the following definitions apply.2.1condensationprecipitation of water vapour on a surface when the surface tempera
34、ture is lower than thedewpoint temperature of the ambient air whereby water is transformed from vapour to the liquidstate of aggregation2.2adsorptionadherence of water vapour molecules to a surface when the surface temperature is higher thanthe dewpoint temperature2.3absorptionaccumulation of water
35、molecules within a material2.4diffusiontransportation of water molecules through a material, produced by a partial pressure differenceNOTE Diffusion results in a balance of partial pressures, whilst flow (such as through leaks, when the dimensionsof such leaks are great enough to provide viscous or
36、laminar flow) always finally results in the balance of the totalpressures.2.5breathingexchange of air between a hollow space and its surroundings, produced by changes oftemperaturePage 5EN 6006834:20023 Procedures for the production and control of humidity3.1 GeneralThere are a great number of humid
37、ity test chambers available, equipped with different methodsof humidity generation and of humidity control.Distilled or deionized water should be used. The water should have a pH value between 6,0and 7,2 and a minimum resistivity of 0,05 MG57.cm.All internal parts of the chamber should be maintained
38、 in a clean condition.In the following subclauses, only the principal methods of generation of humidity arementioned.3.2 Injection of water (spraying)Water is atomized to very fine particles or droplets.The spray produced in this way moistens the air stream before it enters the working space, thegre
39、ater part of the droplets evaporating on the way. Small droplets of water may remain in theairflow.Direct water injection into the working space must be avoided.This simple system gives rapid humidification and requires little maintenance.3.3 Injection of water vapour (steam)Evaporated water (steam)
40、 is blown into the working space of the chamber.This system gives rapid humidification, and is easier maintained (steam valve). However, theresultant heat input may necessitate additional cooling with possible dehumidification effects.3.4 Saturation typeAir is blown through a vessel containing water
41、, thus becoming saturated with vapour.At a fixed airflow, the humidity is controlled by changing the water temperature. If an increaseof humidification is produced by increasing the water temperature, this may cause atemperature rise in the working space and, due to the thermal capacity of the water
42、, theresponse time may be longer. This may necessitate additional cooling with possible de-humidification effects.If bubbles occur they may produce a small amount of spray when bursting.3.5 Surface evaporationThe air is humidified by passing it over a large surface area of water. Different methods a
43、reused, for example repeated air flow over standing water or water-jet scrubbing over a verticalsurface with the air stream in counter current.Page 6EN 6006834:2002In this system, the spray is minimized. The humidity is controlled by changing the watertemperature. Due to the thermal capacity of the
44、water, the response time may be longer.3.6 Aqueous solutionsRelative humidity is generated over standardized aqueous solutions of salts in small sealedchambers at constant temperature. This system is not appropriate for heat-dissipatingspecimens or for specimens absorbing large quantities of moistur
45、e.Salt particles may be deposited on the surface of the test specimens. In some cases, forexample with ammonium salts, these particles may be hazardous to health and may causestress corrosion in some materials.3.7 DehumidificationIn order to control humidity, various dehumidification methods are use
46、d, including coldsurfaces, injection of dry air, desiccants etc.3.8 Control of humidityThe size of the chamber, the humidifier and the response time of temperature/humidity sensorshave important influences on the possible uncertainties of the humidity control system. Thechamber performance can degra
47、de, and therefore uncertainty is affected by the quality ofmaintenance.4 Physical appearance of the effects of humidity4.1 CondensationThe dewpoint temperature depends on the content of water vapour in the air. A directrelationship exists between dewpoint, absolute humidity and vapour pressure.When
48、introducing a specimen into a test chamber condensation may occur if its surfacetemperature is lower than the dewpoint temperature of the chamber air. It may be necessary topre-heat the specimen if condensation has to be prevented.When condensation is required on the specimen during the conditioning
49、 period, thetemperature and the water content of the air shall be raised so that the dewpoint temperatureof the air becomes higher than the surface temperature of the specimen.If the specimen has a low thermal time constant, condensation occurs only if the dewpointtemperature of the air increases very rapidly, or if the relative humidity is very close to 100 %.With the rate of temperature rise prescribed for tests Db, condensation may not occur on verysmall specimens.Condensation may occur on the inner surface of casings subsequent to
